Preparation of monohaloacyl halides

ABSTRACT

A process for the preparation of monohaloacyl halides by halogenating ketenes in the presence of a tertiary phosphate ester.

United States Patent 1 Gash et al.

[ 1 May 13, 1975 PREPARATION OF MONOHALOACYL HALIDES [75] Inventors: Virgil W. Gash; Donald E. Bissing,

both of Ballwin, Mo.

[73] Assignee: Monsanto Company, St. Louis, Mo.

[22] Filed: July 16, I973 [2]] App]. No: 379,899

UNITED STATES PATENTS 2,862,964 l2/l958 Lacey U 260/544 Y 3,763,250 10/1973 Rai et al. 260/544 Y X Primary ExaminerLorraine A. Weinberger Assistant ExaminerRichard D. Kelly Attorney, Agent, or FirmWilliam l. Andress; John L. Young; Donald W. Peterson [5 7] ABSTRACT A process for the preparation of monohaloacyl halides by halogenating ketenes in the presence of a tertiary phosphate ester.

19 Claims, N0 Drawings PREPARATION OF MONOHALOACYL HALIDES This invention relates to the preparation of monohaloacyl halides by the liquid phase halogenation of ketenes, More particularly, this invention relates to the halogenation of ketenes in the presence ofa solvent or a reaction medium that inhibits or prevents the formation of polyhaloacyl halides and minimizes the formation of acyl halides. The term halogenating agent" as used herein includes chlorine, bromine, iodine monochloride, iodine monobromide, bromine monochloride and the like.

The liquid phase halogenation of ketene is well known but the previously known methods of conducting this reaction have resulted in the formation of monohaloacetyl halides contaminated with a considerable proportion of dihaloacetyl halides and polyhalogenated by-products. These earlier methods utilized such solvents as chlorinated benzenes, nitrobenzene, carbon tetrachloride, chloroacetyl chloride, acetyl chloride, 1,2-dichloroethane, acetonitrile, benzonitrile, nitromethane and various other solvents. Each of these solvents had a common shortcoming; that is, they all resulted in the formation of a considerable amount of dihaloacetyl halide, together with the desired product, monohaloacetyl halide. In some of these solvents, the undesired trihaloacetyl halides were also formed. The dihalo derivatives have no commercial utility and their separation from the monohalo derivative is expensive and time consuming. For example, dichloroacetyl chloride has a boiling point of approximately 107C whereas monochloroacetyl chloride has a boiling point of about l05C. This proximity of the boiling points of these two compounds renders their separation exceedingly difficult and also adds an expensive and uneco nomical step to the halogenation process when utilized in the previously know solventsv The monohaloacyl halides produced by the process of this invention are valuable intermediates in the production of herbicidal alpha-haloacetanilides and other products. By contrast, the corresponding diand trihaloacyl halides have no commercial significance. In other words, they are present merely as diluents which detract from the efficacy of the commercially valuable monohaloacyl.,halides. The severity of the problem is evidenced by the fact that all commercially available chloroacetyl chloride is contaminated with appreciable amounts of dichloroacetyl chloride, and in some instances the dichloroacetyl chloride content is as great as six percent.

In accordance with the present invention, the disadvantages of the prior art solvents are overcome by the halogenation of a ketene in the presence ofa solvent of the formula Rs when taken together are alkylene of the empirical formula C,,H wherein n is an integer from 2 through 8, inclusive, and having from two through four carbons, inclusive, in a continuous chain.

The process of the present invention encompasses the halogenation of ketene, i.e., CH =C=O, as well as substituted ketenes, such as methyl ketene, dimethyl ketene, ethyl ketene, diethyl ketene, phenyl ketene, diphenyl ketene, and the like.

Preferred alkoxyalkyl are those groups wherein the aliphatic chains are straight or branched and contain a combined total of from two through eight carbons inclusive. Preferred alkyl are straight or branched aliphatic chains having from one through eight carbons, inclusive.

A preferred substituted alkyl group has the formula C, H R,, wherein R is halo, phenyl, or substituted phenyl, x is an integer from I through 8, inclusive, and y is an integer from I through 3, inclusive. It is more preferred that when R is phenyl then y is l and when x is l and y is 3 then R is halo.

A preferred substituted phenyl group has the formula wherein each Z is independently halo, trihalomethyl, cyano, nitro, lower alkyl or lower alkoxy, and m is an integer from l through 3, inclusive, provided that when each Z is nitro, m cannot exceed 2. Preferred Z groups are halo, nitro, lower alkyl, trifluoromethyl and lower alkoxy,

As employed herein, the terms lower alkyl" and lower alkoxy" designate those groups wherein the aliphatic chain is straight or branched and has from one through five carbons inclusive.

The term halo" designates a halogen atom selected from fluorine, chlorine, bromine and iodine.

In carrying out the process of the present invention, the ketene and the halogenating agent are introduced into the solvent medium where they react to form monohaloacyl halides which are separated from the reaction medium by conventional means such as distillation, preferably at reduced pressure. The process is amenable to either continous or to batch type operationv The operating conditions under which the reaction is conducted are not critical but it is preferred to maintain them within specified limits to maximize the yield of the monohaloacyl halides. In essence, it is only necessary that the reaction mass is liquid under reaction conditions. Because of practical considerations, however, the reaction is normally conducted within the approximate temperature range of 50C to 150C at a pressure from about 50 mm. Hg to about 2 atmospheres. In most instances, however, it is more preferred to operate in a continuous mode at a temperature about 0C and about 1 10C at a pressure between about mm. and about 760 mm. In a batch process it is more preferred to operate in this temperature range at a pressure between about 50 mm. and 760 mm. The reaction of the halogenating agent and the ketene will progress to form substantially pure monohaloacyl halides regardless of the mole ratio of the reactants. The advantages of the present invention are more fully realized, however, when the mole ratio of halogenating agent to ketene is maintained between stantially equimolar rates with the chlorine in sufficient about 0.811 and about 2.021 and optimum results are excess that a slight trace of chlorine was detectable in obtained with mole ratios of halogenating agent to kethe exhaust from the vacuum system. After about 3 tene between about 1:1 and about 1.311. The presence hours, the addition of the reactants was terminated. At of solvent of the present invention in the reaction mass 5 the termination of the reaction, the ratio of the solvent minimizes the formation of acyl halides and substanto the sum of the solvent and product was about 0.5. tially eliminates the formation of dihaloacyl halides and The reaction mixture contained essentially solvent, other polyhalogenated by-products. chloroacetyl chloride (HALOACYL CHLORIDE) and In accordance with the present invention, the solvent acetyl chloride. The reaction mixture contained only a can constitute substantially all or only a minor portion trace, i.e., less than 0.1% of dichloroacetyl chloride of the reaction medium. The benefits of the present in- (DIHALOACYL HALIDE) and other polychlorinated vention are most pronounced when the solvent weight by-products. Upon distillation to separate the pure ratio is high but substantial benefits are realized even hl tyl chloride, the mole percent yield of chlorowhen the solventis present in relatively small amounts. acetyl hl id w determined to be 97%, together The un sira l polyhal g n yl halides are with about 3% acetyl chloride. Analysis of the solvent formed only in minute amounts even when the reaction f i h w d th t about 147 grams of solvent were mass Contains a 10W Path) of Solvent and y are present. This high level of solvent recoverability indistehtletly excluded at the higher Tahoe The Weight cates that negligible chlorination or other side reac- Yahe 0f the Solvent to the Sum 0f the Solvent and the tions involving solvent occurred during the reaction product, i.e., the solvent weight ratio, can vary from l di to Solvent about 0.05:1 to about 0.99: 1. In fact, during the normal l h h i hi example h eactign m wa t course of a batch reaction, the solvent weight ratio diagitated, agitation i ti l and can be used when minishes with the formation of the product which bed d d di upon reactor de ign and the hoi e Comes mixed with the Solvent forming the reaction ofreactants,i.e.,ketene and halogenating agent. When th the Practice of the Continuous Preeess, the bromine is the halogenating agent, it is preferred to agi- VEHI Weight ratio can h maintained constant OT varied [ate the reaction mass but good results are 3150 0b. to desired le s. tained without agitation.

The invention will be more clearly understood from Following the general pmmdure f E l 1 b the following detailed description of Specific examples with conditions and materials changed as noted in thel'eotthe examples and throughout the Specifica Table 1 the indicated products are obtained. The line all Proportions are expressed in Parts by Wetght titles of Table 1 are shown in parenthesis in the descrip- 1685 otherwise indicated tion of Example 1 where appropriate.

EXAMPLE l ln Examples 3 through 5 the yield of haloacyl halide About 149 parts (SOLVENT AMOUNT) of triethyl g n a v pe a the m0 n of phosphate (SOLVENT) were charged into a i bl dihaloacyl halide IS minimized giving a haloacyl halide reaction vessel provided with a gas outlet, temperature P y otgreatel' than P l' lh Example 2 the recording means and two gas spargers below the level yield Of iodoacetyl chloride 15 about -90 percent. of the solvent. With the reaction vessel at 69 mm. of H Diiodoacetyl chloride is extremely unstable and therere u e (PREssURE) nd with th ti di 40 fore is not found in the reaction mass of Example 2.

TABLE 1 EXAMPLE NO. 2 3 4 5 SOLVENT Triethyl phosphate Tris-(Z-chloro- Triethyl Triethyl ethyl)phosphate phosphate phosphate PRESSURE 100 100 atmospheric atmospheric (mm. Hg) TEMPERATURE 5-10 20 30 5O KETENE Ketene Ketcnc Methyl ketene Phenyl ketene HALOGENAT- [NG AGENT Iodine monochloride Chlorine Chlorine Chlorine SOLVENT AMOUNT(parts) 200 100 150 32 HALOGEN AMOUNT (parts) 179 148 22 KETENE AMOUNT (parts) 42 48 36 HALOACYL HALlDE lodoacetyl chloride Chloroacetyl Alphachloro Alphachlorophenylchloride propionyl chloride acetyl chloride DIHALOALYL HALIDE Dichloroacetyl Alpha, alpha- Alpha, alphadichlorochloride dichloropro phenylacctyl chloride pionyl chloride maintained at a temperature of approximately 14 to S Trimethyl phosphate, triphenyl phosphate, tri-Z- 16C (TEMPERATURE), ketene (KETENE) and methoxyethyl phosphate. diethyl propyl phosphate, chlorine (HALOGENATING AGENT) were introtris-2-pheny1ethyl phosphate, tripara-toly1 phosphate duced through separate spargers at constant and suband ethyl ethylene phosphate may be substituted for tiiethtl phosphate as the solvent in lisample l to give similar results laXAMlll: (w

To a reactor fitted with spargers and thermometer was added HM parts of tri-n-butyl phosphate. (hloriue and keteuc \vcre sparged into the reactor at 73 mm, of Hg pressure with the temperature maintained at about Zll( for approximately 3 hours The chlorine intro duced into the reactor during this time was sufficient to maintain a slight excess with respect to the ketene. Analysis of the product gave the following results:

brominations in accordance with this invention by using a solution ofbromine in the solvent and then adding the resulting solution to the system,

Although the invention has been described with re- 5 spect to specific modification. the details thereof are not to be construed as limitations except to the extent indicated in the following claims.

What is claimed is:

l. A process for the preparation of a monohaloaeyl halide which comprises reacting a ketene selected from the group consisting of unsubstituted ketene methyl ketene. dimethyl ketene, ethyl ketene. diethyl ketene. phcnyl ketene and diphenyl ketene and a halogenating agent selected from the group consisting of chlorine.

c t v v l r v hal ?"z tmxg'w l5 bromine tfltlltlc iodlne monochloride, iodine monoi'ieta of tlt'tlll Ll\lt lltlt (percent) a s bromide and bromine monochloride in the presence of \aeltl of dichloroacet l chlorldc (percent! 4 u sflvunl f th f m Soht-nt recint'red lgramsl l5l.2

ln order to illustrate the advantages of the solvents of m the present invention. the procedure of the foregoing 0 Example l was substantially duplicated using other solg R \ents m er a range of reaction pressures. The percent I yields thus obtained. together with the results of repre- O sentatne emmples of this invention are tabulated N belo in Table II R 'l'ABltl-I ll (hloroacetyl Acetyl Dichloro- Solvent Reactor Chloride (hloride acetyl Recovered Pressure Yield Purity Yield Chloride l'/r l (mm. of Hg! Sohent (it (it (it Yicldl /l I E\amp|c l 97 99.9 3 at 9&4 69 [-lsample 897 9&4 9.8 (I74 97 7] Eth \l Acetate 88 978 ll I5 84 73 Ethyl Acetate 92 9h 5 3 78 atmospheric Carbon Tctra- 42 69 43 I5 75 atmospheric Chloride l.Z-Diehlon 5] 4| 24 atmospheric ethylene Meth \l Acetate 94 4 4 X8 atmospheric Acetunitrile 4e 83 47 7 (16 atmospheric Nitromethaue -18 7-4 3) 13 75 atmospheric n-Butyl Acetate 82 95 15 3 R4 atmospheric n-Hexyl Acetate XI )5 l5 4 83 atmospheric Benzonitrile 87 94 9 4 93 atmospheric By comparison of the same procedure utilizing other wherein each R is independently alkoxyalkyl. alkyl, solvents it is self-evident that the solvents of the pressubstituted alkyl of the formula C H .e,, R ent invention substantially suppress the formation of wherein R is halo, phenyl, or substituted phenyl of the polychloroacetyl chlorides and minimize the formation formula of acetyl chloride. The separation of pure chloroacetyl chloride from acetyl chloride and the solvent by fractionation presents no problem because of the wide divergence in boiling points of these compounds.

The improvement effected by the solvents of the present invention is also evidenced in the better than S;

95% recovery of the solvent for recycle purposes This y I provides greatly improved economy of operation. It is where!" each L mdependemly hal0- mhalomelhyL also evident from the high percent recovery of the soll kwer alkyl f" lower alkoxyw and vent of this invention that the beneficial effect exerted mteger f m I through mcluswei when by these solvents is due to the intrinsic nature of the each 2 h Calmm F meg6r fmm chfimical Structure of the Sahel 1 through inclusive, and y is tin integer from I The beneficial results of the present invention are oblhmugh mcluswephenyl or Substlwled Phenyl of tained in like manner with other solvents of this inventhe formula tion as well as with the other aforementioned halogenating agents Bromine can be introduced into the sys- 6S 7 tern as the liquid, combined with the solvent in solution, or in the gaseous state below the surface of the re action mass. In most instances it is preferred to conduct wherein each Z is independently halo, trihalomethyl, cyano, nitro, lower alkyl or lower alkoxy, and m is an integer from I through 3, inclusive, provided that when each Z is nitro, m cannot exceed 2 or two Rs when taken together are alkylene of the empirical formula C H- wherein n is an integer from 2 through 8, inclusive, and having from two through four carbons, inclusive, in a continuous chain.

2. A process of claim 1 wherein each R is alkoxyalkyl.

3. A process of claim 1 wherein each R is substituted phenyl.

4. A process of claim 1 wherein each R is phenyl.

5. A process of claim 1 wherein each R is substituted alkyl.

6. A process in accordance with claim 1 wherein one R is alkyl and the two other Rs, taken together, are alkylene.

7. A process in accordance with claim 1 wherein each R is alkyl.

8. A process in accordance with claim 1 wherein the halogenating agent is chlorine.

9. A process in accordance with claim 1 wherein the halogenating agent is bromine.

10. A process of claim 1 wherein the keter is unsubstituted ketene.

ll. A process of claim 10 wncrein the halogenating agent is chlorine.

12. The process of claim 11 wherein each R is alkyl.

13. The process of claim 1 wherein the solvent is trin-butyl phosphate.

14. The process of claim I wherein the solvent is tri- 2-methoxyethyl phosphate.

15. The process of claim I wherein the solvent is tris- (Z-chloroethyl) phosphate.

16. The process of claim I wherein the solvent is triethyl phosphate.

17. A process of claim 16 wherein the ketene is unsubstituted ketene.

18. A process of claim 17 wherein the halogen is chlorine.

19. Process according to claim 7 wherein said monohaloacyl halide is chloroacetyl chloride. 

1. A PROCESS FOR THE PREPARATION OF A MONOHALOACYL HALIDE WHICH COMPRISES REACTING A KETENE SELECTED FROM THE GROUP CONSISTING OF UNSUBSTITUTED KETENE, METHYL KETENE, DIMETHYL KETENE, ETHYL KETENE, DIETHYL KETENE, PHENYL KETENE AND DIPHENYL KETENE AND A HALOGENATING AGENT SELECTED FROM THE GROUP CONSISTING OF CHLORINE, BROMINE, IODINE, IODINE MONOCHLORIDE, IODINE MONOBROMIDE AND BROMINE MONOCHLORIDE IN THE PRESENCE OF A SOLVENT OF THE FORMULA
 2. A process of claim 1 wherein each R is alkoxyalkyl.
 3. A process of claim 1 wherein each R is substituted phenyl.
 4. A process of claim 1 wherein each R is phenyl.
 5. A process of claim 1 wherein each R is substituted alkyl.
 6. A process in accordance with claim 1 wherein one R is alkyl and the two other R''s, taken together, are alkylene.
 7. A process in accordance with claim 1 wherein each R is alkyl.
 8. A process in accordance with claim 1 wherein the halogenating agent is chlorine.
 9. A process in accordance with claim 1 wherein the halogenating agent is bromine.
 10. A process of claim 1 wherein the keter is unsubstituted ketene.
 11. A process of claim 10 wherein the halogenating agent is chlorine.
 12. The process of claim 11 wherein each R is alkyl.
 13. The process of claim 1 wherein the solvent is tri-n-butyl phosphate.
 14. The process of claim 1 wherein the solvent is tri-2-methoxyethyl phosphate.
 15. The process of claim 1 wherein the solvent is tris-(2-chloroethyl) phosphate.
 16. The process of claim 1 wherein the solvent is triethyl phosphate.
 17. A process of claim 16 wherein the ketene is unsubstituted ketene.
 18. A process of claim 17 wherein the halogen is chlorine.
 19. Process according to claim 7 wherein said monohaloacyl halide is chloroacetyl chloride. 